## Random
### getString 
获取6位随机字符串

```javascript
function getStr () {
    return Math.random().toString(36).substring(7);
}
```

### getRandNum 

```javascript
export function getRandNum(min, max) {
  return Math.random() * (max - min) + min;
}
```

### getRandInt  

```javascript
export function getRandInt(min, max) {
  min = Math.ceil(min);
  max = Math.floor(max);
  return Math.floor(Math.random() * (max - min)) + min; 
}
```